Hello.
So my family have had a black labrador named Bradley for about a year now.
When we first got him, he was as you'd expect, going to the toilet everywhere, whining constantly, always wanting attention, etc.
We took him to a session of training classes around October time. He learned to sit, heel, the basics really but would only ever do it if treats were held right in front of its face, which is not really abnormal I think.
We've been trying on and off to train him ever since the classes, and things don't seem to be working. I mean, he'll do things when there's the immediate promise of reward and only then. His whole attitude is just terrible, he has no respect for any of us.
We've been told the usual things, like making sure that we eat first at mealtimes, only feed him so much, walk through doors first, etc. but they don't really seem to be working.
He also seems to enjoy jumping up and biting. He's a very big dog, even if he was fully grown (my friend has adult labs and they are quite a bit smaller, as are other labs nearby). He's been doing it for a while and we've been trying to train him out of it by shouting NO!, stopping play, leaving and then coming back a few minutes later with a completely changed attitude, which seems to work sometimes, but very often his mood will completely change within a second, eg. he'll start to bite during play/petting, for example.

I am 17 and pretty tall, at least 6ft2, and earlier this evening he jumped up to my face. I would be ok if he tried to bite me, I am just very worried if he tried to bite my sisters or my mum, all much smaller, and my mum is the only one at home during the day, looking after my 2y/o brother.
We don't want to wait until its too late, but at the same time don't want to just give up on the dog and get rid of him too soon without trying to stop this behaviour.
He's been 'fixed' so it's unlikely to be anything to do with hormones.

Any help will be much appreciated.